There is no imitation; answer D is the one! The other sentences, however, can be correctly completed with words inspired by the name of animals. In the first sentence, Levi has put away, or "squirreled," money for future use, just as a squirrel stores nuts for the winter. In sentence B, it's most likely that negative thoughts were "dogging" Nathan, or worrying him as if by pursuit with dogs. In sentence C, the kids are most likely to be "monkeying" around with the smartphone, as in fooling around with it. That leaves Anabel and her sisters who were copying her voice, or "aping" it.